WO2009110037A1

WO2009110037A1 - Method of controlling exhaust gas in oxygen combustion boiler and apparatus therefor

Info

Publication number: WO2009110037A1
Application number: PCT/JP2008/000475
Authority: WO
Inventors: 照下修平; 山田敏彦; 渡辺修三; 内田輝俊
Original assignee: 株式会社Ihi; 電源開発株式会社
Priority date: 2008-03-06
Filing date: 2008-03-06
Publication date: 2009-09-11
Also published as: AU2008352213B2; EP2251599B1; JP5208195B2; PL2251599T3; AU2008352213A1; ES2532503T3; JPWO2009110037A1; US8601960B2; CN102016419A; EP2251599A1; CN102016419B; EP2251599A4; US20110132243A1

Abstract

An exhaust gas control apparatus for an oxygen combustion boiler (4) including a boiler (4) provided with a burner (6) and a two-stage combustion port (7); a primary recirculation line (12) for feeding pulverized coal obtained by a mill (3) to the burner (6) of the boiler (4) by a primary recirculating exhaust gas; a secondary recirculation line (14) for feeding another portion of recirculating exhaust gas to a wind box (5) of the boiler (4); an oxygen production equipment (23); a direct supply line (25) for direct supply of a portion of oxygen produced by the oxygen production equipment (23) to the burner (6); and a secondary oxygen mixing line (24) for supply of another portion of oxygen produced by the oxygen production equipment (23) to the secondary recirculation line (14). The exhaust gas control apparatus comprises an oxygen supply line (26) for supply of oxygen to the two-stage combustion port (7) of the boiler (4) and flow rate regulators (20,27) for regulation of oxygen concentration provided along the oxygen supply line (26).

Description

Exhaust gas control method and apparatus for oxyfuel boiler

The present invention relates to an exhaust gas control method and apparatus for an oxyfuel boiler.

In recent years, it has been clarified that the increase in the concentration of carbon dioxide (CO ₂ ) in the atmosphere is one of the main causes of global warming, which has been widely taken up as a global environmental problem. Is attracting attention as a fixed emission source of these substances, but oil, natural gas, and coal are used as fuels for thermal power generation. Has been.

Coal has a higher carbon content than natural gas and petroleum, and also contains other components such as hydrogen, nitrogen, and sulfur, and ash that is inorganic. Becomes nitrogen (about 70%), and other gases such as carbon dioxide CO ₂ , sulfur oxide SOx, nitrogen oxide NOx, oxygen (about 4%), and fine particles such as unburned matter and ash. Become. Therefore, exhaust gas is subjected to exhaust gas treatment such as denitration, desulfurization, and dedusting, and NOx, SOx, and fine particles are discharged from the chimney to the atmosphere so as to be below the environmental emission standard value.

The NOx in the exhaust gas includes thermal NOx generated by oxidizing nitrogen in the air with oxygen and fuel NOx generated by oxidizing nitrogen in the fuel. Conventionally, a combustion method for reducing the flame temperature has been adopted for reducing thermal NOx, and a combustion method for forming an excess fuel region for reducing NOx in the combustor has been adopted for reducing fuel NOx. .

In addition, when a fuel containing sulfur such as coal is used, SOx is generated in the exhaust gas by combustion. Therefore, the fuel is removed with a wet or dry desulfurization device.

On the other hand, carbon dioxide generated in a large amount in exhaust gas is desired to be separated and removed with high efficiency. As a method for recovering carbon dioxide in exhaust gas, a method of absorbing it in an absorbing solution such as an amine, However, although an adsorption method for adsorbing to a solid adsorbent, a membrane separation method, or the like has been studied, all have low conversion efficiency and have not yet been practically used for CO ₂ recovery from a coal fired boiler.

Therefore, as an effective method for simultaneously achieving the problem of separation of carbon dioxide in exhaust gas and suppression of thermal NOx, a method of burning fuel with oxygen instead of air has been proposed (for example, Patent Documents 1 to 4). Etc.).

When coal is burned with oxygen, the generation of thermal NOx disappears, and most of the exhaust gas becomes carbon dioxide, and other fuel NOx, SOx, and gas containing unburned matter, so by cooling the exhaust gas, the carbon dioxide becomes It becomes relatively easy to liquefy and separate.

Here, the structure of the boiler that performs air combustion will be described. There are various types of boilers, and one of them is provided with a plurality of rows of burners arranged in the furnace width direction and a plurality of stages in the vertical direction. A two-stage combustion port (so-called OAP (Over Air Port)) is provided at each upper required position corresponding to each row of burners, and two-stage combustion air blown out from the two-stage combustion port Stage combustion is performed.
JP-A-5-231609 JP 2001-235103 A Japanese Patent Laid-Open No. 5-168883 JP 2007-147162 A

However, ordinary boilers and two-stage combustion boilers have a problem in that it is difficult to control the amount of NOx, CO, and the like in the exhaust gas discharged from the boiler. Conventionally, it has been studied to control the amount of unburned components such as NOx and CO in the exhaust gas by changing the air flow rate ratio, but it has not been possible to control it appropriately.

In view of such circumstances, the present invention aims to provide an exhaust gas control method and apparatus for an oxyfuel boiler that controls the amount of NOx in exhaust gas discharged from the boiler and the amount of unburned exhaust gas. is there.

The present invention introduces a boiler having a burner and a two-stage combustion port, and a part of the exhaust gas discharged from the boiler and recirculated to the mill as a primary recirculation exhaust gas, and finely pulverized by the mill A primary recirculation system for supplying charcoal to the boiler burner by the primary recirculation exhaust gas, a secondary recirculation system for supplying another part of the recirculated exhaust gas to the boiler wind box, an oxygen production device, A direct supply system for supplying a part of oxygen produced by the oxygen production apparatus directly to the burner, and a second supply system for supplying another part of the oxygen produced by the oxygen production apparatus to the secondary recirculation system. An exhaust gas control method for an oxyfuel boiler having a secondary oxygen mixing system, the exhaust gas control method for an oxyfuel boiler comprising adjusting oxygen concentration by supplying oxygen to a two-stage combustion port of the boiler Also related to It is.

In the oxyfuel boiler exhaust gas control method described above, when the unburned amount of exhaust gas is an allowable value and the overall NOx concentration is lowered, the amount of recirculated exhaust gas to the two-stage combustion port is adjusted to increase. When reducing the oxygen concentration at the stage combustion port and increasing the overall heat recovery of the boiler or lowering the unburned content of the entire exhaust gas, reduce the amount of recirculated exhaust gas to the second stage combustion port. It is preferable to adjust to increase the oxygen concentration to the two-stage combustion port.

In the exhaust gas control method for an oxyfuel boiler, it is preferable to adjust the oxygen concentration for each of the two-stage combustion ports with respect to the plurality of two-stage combustion ports arranged in the boiler.

Further, in the exhaust gas control method for the oxyfuel boiler, it is preferable to supply a part of the exhaust gas supplied through the secondary recirculation system to the second stage combustion port of the boiler.

The present invention introduces a boiler having a burner and a two-stage combustion port, and a part of the exhaust gas discharged from the boiler and recirculated to the mill as a primary recirculation exhaust gas, and finely pulverized by the mill A primary recirculation system for supplying charcoal to the boiler burner by the primary recirculation exhaust gas, a secondary recirculation system for supplying another part of the recirculated exhaust gas to the boiler wind box, an oxygen production device, A direct supply system for supplying a part of the oxygen produced by the oxygen production apparatus directly to the burner, and a second supply system for supplying another part of the oxygen produced by the oxygen production apparatus to the secondary recirculation system. An exhaust gas control device for an oxyfuel boiler having a secondary oxygen mixing system, wherein the oxygen supply system is configured to supply oxygen to the two-stage combustion port of the boiler and the oxygen supply system to adjust the oxygen concentration Equipped with a flow regulator Exhaust gas control apparatus of an oxyfuel combustion boiler which consists was, it relates to a.

In the above oxyfuel boiler exhaust gas control device, when the unburned amount of exhaust gas is an allowable value and the overall NOx concentration is lowered, the amount of recirculated exhaust gas to the two-stage combustion port is increased by the flow regulator. When adjusting to reduce the oxygen concentration to the two-stage combustion port and increase the overall heat recovery of the boiler or to reduce the unburned content of the entire exhaust gas, the flow regulator adjusts the oxygen concentration to the two-stage combustion port. It is preferable that the oxygen concentration to the two-stage combustion port is increased by adjusting in a direction to reduce the amount of recirculated exhaust gas.

Further, in the exhaust gas control apparatus for an oxyfuel boiler, a plurality of two-stage combustion ports arranged in the boiler are provided, and a plurality of branch oxygen supply systems are provided so as to adjust the oxygen concentration for each of the two-stage combustion ports. It is preferable.

Also, the exhaust gas control device for the oxyfuel boiler preferably includes a tertiary recirculation system for supplying a part of the exhaust gas supplied through the secondary recirculation system to the second combustion port of the boiler.

According to the exhaust gas control method and apparatus for an oxyfuel boiler of the present invention, in a boiler provided with a burner and a two-stage combustion port, oxygen is supplied from the two-stage combustion port to adjust the oxygen concentration, An excellent effect that the NOx concentration and the unburned amount of the exhaust gas can be controlled can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole schematic block diagram which shows the embodiment which implements this invention. It is a conceptual diagram which shows the tertiary recirculation system path and oxygen supply system path which are connected to the port for two-stage combustion of an oxyfuel boiler. It is a flowchart which shows the flow of control in the example which implements this invention. It is a diagram which shows the operation | use range in the example which implements this invention.

Explanation of symbols

3 Mil 4 Boiler 5 Wind Box 6 Burner 7 Port for Second Stage 9 Air Preheater 10 Exhaust Gas Treatment Device 12 Primary Recirculation System 14 Secondary Recirculation System 19 Tertiary Recirculation System 20 Third Flow Controller Regulator)
23 Oxygen production equipment 24 Secondary oxygen mixing system path 25 Direct supply system path 26 Oxygen supply system path 26a First branch oxygen supply system path 26b Second branch oxygen supply system path 26c Third branch oxygen supply system path 26d First Fourth branch oxygen supply system 27 Oxygen flow controller (flow controller)
28 Oxygen concentration meter

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 to 4 show an example of an embodiment of the present invention, where 1 is a coal bunker that stores coal, 2 is a coal feeder that cuts out coal stored in the

coal bunker

1, and 3 is supplied from the coal feeder 2. 4 is an oxyfuel boiler, 5 is a wind box attached to the

boiler

4, 6 is disposed in the wind box 5 and combusts pulverized coal supplied from the mill 3. A burner 7 is a two-stage combustion port (so-called OAP (Over Air Port)) disposed at a required position above the burner 6 in the

boiler

4, 8 is an exhaust gas line through which exhaust gas discharged from the boiler 4 flows, and 9 is an exhaust gas line 8 is an air preheater for exchanging heat between the exhaust gas flowing through the primary recirculation exhaust gas and the secondary recirculation exhaust gas, and 10 is a desulfurizer or dust collector for treating the exhaust gas that has passed through the air preheater 9. Exhaust gas treatment device such as 11, 11 is a forced air blower (FDF) that pumps the exhaust gas purified by the exhaust gas treatment device 10 as a primary recirculation exhaust gas and a secondary recirculation exhaust gas, and 12 is the exhaust gas pressure fed by the forced air blower 11. A primary recirculation system that preheats a part of it as primary recirculated exhaust gas with the air preheater 9 and leads it to the

mill

3, 13 is a first flow controller for adjusting the flow rate of the primary recirculated exhaust gas, and 14 is a forced air blower A secondary recirculation system 15 for preheating the other part of the exhaust gas pumped by 11 as a secondary recirculation exhaust gas by the air preheater 9 and leading it to the wind box 5; 15 adjusts the flow rate of the secondary recirculation exhaust gas second flow regulator for, 16 recovery apparatus for recovering the CO ₂ or the like incorporating the exhaust gas is purified by a exhaust

gas processing system

10, 17 to attract the exhaust gas provided downstream of the exhaust gas treatment apparatus 10 induction Ventilator (IDF), 18 is an exhaust gas is attracted by the induced draft fan 17 is purified by the exhaust gas treatment apparatus 10 is a stack of atmospheric discharge.

Here, the burners 6 of the boiler 4 are arranged in a plurality of rows (four rows in FIG. 2) in the furnace width direction and in a plurality of rows (two steps in FIG. 2) in the vertical direction. The combustion port 7 is formed with a first port portion 7a, a second port portion 7b, a third port portion 7c, and a fourth port portion 7d at a required position above the burner 6 so as to correspond to the burners 6 in each row. Yes.

The secondary recirculation path 14 is provided with a tertiary recirculation path 19 that branches from between the second flow rate regulator 15 and the wind box 5 and supplies part of the exhaust gas to the second-stage combustion port 7. The tertiary recirculation path 19 further includes a first branch recirculation path 19a, a second branch recirculation path 19b, a third branch recirculation path 19c, and a fourth branch recirculation from the midway position. It branches to the system path 19d and corresponds to the first port part 7a, the second port part 7b, the third port part 7c, and the fourth port part 7d. Here, the two-stage combustion port 7 is not limited to four rows, and may be another plurality of rows. When the second-stage combustion port 7 is another plurality of rows at the same time, a branch recirculation system is provided. It is comprised so that it can respond | correspond to several rows. In FIG. 1, the branch recirculation paths 19a, 19b, 19c, 19d are denoted by reference numeral 19a.

The tertiary recirculation system 19 has a third flow rate controller 20 between the branch position from the secondary recirculation system 14 and the branch position to the branch recirculation paths 19a, 19b, 19c, 19d. The first branch recirculation system path 19a, the second branch recirculation system path 19b, the third branch recirculation system path 19c, and the fourth branch recirculation system path 19d are respectively provided with flow rates. Individual adjusters 21a, 21b, 21c, and 21d are provided, and individual oximeters 22a, 22b, 22c, and 22d are provided. In FIG. 1, the individual flow rate controllers 21a, 21b, 21c, and 21d are indicated by reference numeral 21a, and the individual oxygen concentration meters 22a, 22b, 22c, and 22d are indicated by reference numeral 22a.

The overall configuration includes an oxygen production device 23 for producing oxygen by taking in air, and a secondary that supplies a part of the oxygen produced by the oxygen production device 23 to the secondary recirculation system 14 as secondary oxygen. An oxygen mixing system path 24 is provided, and an oxygen flow rate controller (not shown) is disposed in the secondary oxygen mixing system path 24. Here, in the illustrated example, the case where the secondary oxygen is supplied to the secondary recirculation system 14 on the downstream side of the air preheater 9 is exemplified, but the secondary oxygen may be supplied to the upstream side of the air preheater 9.

Further, the overall configuration is provided with a direct supply system path 25 for directly supplying other part of the oxygen produced by the oxygen production apparatus 23 to the burner 6 as direct supply oxygen. Is provided with a direct supply amount regulator (not shown).

Further, the overall configuration includes a branching position to the secondary oxygen mixing system path 24 and the direct supply system path 25 so that the remaining oxygen produced by the oxygen production apparatus 23 is supplied to the two-stage combustion port 7 of the boiler 4. The oxygen supply system path 26 branches from between the first branch oxygen supply system path 26a, the second branch oxygen supply system path 26b, and the third branch from the middle position. Branches into the oxygen supply system path 26c and the fourth branch oxygen supply system path 26d, the first branch recirculation system path 19a, the second branch recirculation system path 19b, the third branch recirculation system path 19c, The four branch recirculation paths 19d are connected. Further, the oxygen supply system path 26 is provided with an entire oxygen flow rate regulator 27 on the upstream side, and an entire oxygen concentration meter 28 is disposed on the downstream side, and the first branch oxygen supply system path 26a and the second oxygen supply system path 26a. The branch oxygen supply system path 26b, the third branch oxygen supply system path 26c, and the fourth branch oxygen supply system path 26d are respectively provided with individual oxygen

flow rate regulators

29a, 29b, 29c, and 29d. In FIG. 1, the oxygen supply system path 26 is connected by A, the branched oxygen

supply system paths

26a, 26b, 26c, and 26d are denoted by reference numeral 26a, and the oxygen flow rate

individual controllers

29a, 29b, 29c, and 29d are This is indicated by reference numeral 29a.

Here, the third flow regulator 20 of the tertiary recirculation system 19, the individual flow controller 21 a of the first branch recirculation system 19 a, the individual flow controller 21 b of the second branch recirculation system 19 b, The individual flow rate regulator 21c of the third branch recirculation path 19c, the individual flow rate regulator 21d of the fourth branch recirculation path 19d, and the overall oxygen flow rate regulator 27 of the oxygen supply path 26, the first An oxygen flow rate individual controller 29a of the branch oxygen supply system path 26a, an oxygen flow rate individual controller 29b of the second branch oxygen supply system path 26b, an oxygen flow rate individual controller 29c of the third branch oxygen supply system path 26c, a fourth The individual oxygen flow rate regulators 29d of the branched oxygen supply system 26d are all connected to the control unit 30, and the control unit 30 is connected to the NOx concentration between the boiler 4 and the air preheater 9 in the exhaust gas line 8. 31 in total, oxygen in the oxygen supply line 26 The concentration meter 28, the individual oxygen concentration meter 22a of the first branch recirculation system 19a, the individual oxygen concentration meter 22b of the second branch recirculation system 19b, and the individual of the third branch recirculation system 19c The processing means Sa is controlled so as to control the

respective regulators

20, 21a to 21d, 27, 29a to 29d on the basis of signals from the oxygen concentration meter 22c and the individual oxygen concentration meters 22d of the fourth branch recirculation system 19d. , Sb. Here, the signal input to the control unit 30 may be other data, and is particularly limited if each of the

regulators

20, 21a to 21d, 27, 29a to 29d is controlled in accordance with the situation of the boiler 4. It is not something.

Next, the operation of the illustrated example will be described.

In the boiler 4, the coal stored in the coal bunker 1 is input to the mill 3 by the coal feeder 2, and the coal is pulverized and pulverized into the coal in the mill 3, and the exhaust gas treatment is performed by the forced air blower 11 (FDF). The primary recirculated exhaust gas, which is part of the exhaust gas taken out from the downstream of the apparatus 10, is introduced into the mill 3 through the primary recirculation system 12, and the coal fed into the mill 3 is dried by the primary recirculated exhaust gas. The finely pulverized coal is conveyed to the burner 6 of the boiler 4.

On the other hand, the wind box 5 of the boiler 4 is supplied with another part of the exhaust gas from the forced air blower 11 as a secondary recirculation exhaust gas by the secondary recirculation system 14 and the two-stage combustion of the boiler 4. A part of the secondary recirculation gas (exhaust gas) supplied through the secondary recirculation path 14 is supplied to the port 7 for the tertiary recirculation path 19 and the respective branch recirculation paths 19a, 19b, 19c, 19d. Supplied by

Further, a part of the oxygen produced by the oxygen production apparatus 23 is supplied to the secondary recirculation system 14 by the secondary oxygen mixing system 24, and another part of the oxygen from the oxygen production apparatus 23 is directly supplied. The oxygen is supplied directly to the burner 6 by the supply system 25, and the remaining oxygen from the oxygen production apparatus 23 is further supplied via the oxygen supply system 26 and the respective branched

oxygen supply systems

26a, 26b, 26c, 26d. Supplied by the respective branch recirculation paths 19a, 19b, 19c, 19d. Here, the oxygen supplied to the two-stage combustion port 7 via the oxygen supply system 26 or the like may be supplied together with the exhaust gas or may be supplied directly without being mixed with the exhaust gas.

Accordingly, the pulverized coal supplied from the mill 3 to the burner 6 by the primary recirculation exhaust gas is mixed with the secondary recirculation gas supplied to the wind box 5 after being mixed with oxygen, and the direct supply oxygen supplied directly to the burner 6. And the exhaust gas mixed with oxygen and supplied to the two-stage combustion port 7 is combusted. The exhaust gas generated by combustion preheats the primary recirculation exhaust gas and the secondary recirculation exhaust gas by the air preheater 9, and further, after being processed by the exhaust gas treatment device 10, a part thereof is introduced to the forced draft fan 11 and the recovery device 16. The remainder is attracted by the induction fan 17 (IDF) and released from the chimney 18 to the atmosphere. The exhaust gas taken into the recovery device 16 is recovered such as CO ₂ .

Here, since the combustion state of the boiler 4 varies depending on various conditions, the control unit 30 can adjust the NOx concentration, the unburned amount of the exhaust gas such as CO, and the furnace heat recovery, depending on the combustion state of the boiler 4. In the control means Sa, data is obtained from the NOx concentration meter 31, the oxygen concentration meter 28 of the oxygen supply system 26, and the individual oxygen concentration meters 22a, 22b, 22c, 22d of the respective branch recirculation systems 19a, 19b, 19c, 19d. And determining the combustion state of the boiler 4 including the operator's request and the like, and the control means Sb of the control unit 30 controls the third flow rate regulator 20 of the tertiary recirculation system 19 to each branch recirculation system. Individual flow rate regulators 21a, 21b, 21c, 21d, oxygen flow rate regulator 27 for the entire oxygen supply system 26, and individual oxygen

flow rate regulators

26a, 26b, 26c, 26d for each branch oxygen supply system 9a, 29b, 29c, and controls the supply amount of oxygen to adjust the 29d to the two-stage combustion port 7.

Specifically, when the unburned amount of the exhaust gas is an allowable value and there is a request to reduce the total NOx concentration (step Sa1), the oxygen concentration meter 28 in the oxygen supply system path 26 is measured, and the third The flow rate regulator 20 and the oxygen flow rate regulator 27 are operated to reduce the oxygen supplied to the two-stage combustion port 7 (step Sb1), and the oxygen concentration is reduced to lower the overall NOx concentration. Further, when there is a request to increase the overall heat recovery of the boiler 4 (step Sa2) or when there is a request to reduce the amount of unburned components contained in the entire exhaust gas (step Sa3), the oxygen supply path While measuring the oxygen concentration meter 28 of 26, the third flow rate regulator 20 and the oxygen flow rate regulator 27 are operated to increase the oxygen supplied to the two-stage combustion port 7 (step Sb2), and the oxygen concentration is increased. Increase the overall heat recovery of the boiler 4 or reduce the amount of unburned emissions contained in the entire exhaust gas.

Further, when the unburned amount of the exhaust gas is an allowable value and there is a request to reduce the NOx concentration in a part of the furnace of the boiler 4 (particularly in the furnace width direction) (step Sa4), the respective branched oxygen supply lines 26a, While measuring the oxygen concentration meters 22a, 22b, 22c, and 22d of 26b, 26c, and 26d, the corresponding individual flow rate controllers 21a, 21b, 21c, and 21d, and the respective oxygen flow rate

individual controllers

29a, 29b, 29c, and 29d are provided. By operating, the oxygen supplied to the port portion of the two-stage combustion port 7 is reduced (step Sb3), the oxygen concentration is reduced, and the NOx concentration is lowered in a part of the furnace of the boiler 4 (particularly in the furnace width direction). Furthermore, when there is a request to increase the heat collection in a part of the furnace of the boiler 4 (step Sa5), or when there is a request to reduce the amount of unburned components contained in the exhaust gas in a part of the furnace (step Sa6), While measuring the oxygen concentration meters 22a, 22b, 22c, and 22d of the respective branched

oxygen supply lines

26a, 26b, 26c, and 26d, the corresponding individual flow rate controllers 21a, 21b, 21c, and 21d, and the respective oxygen flow rate individual adjustments The oxygen supplied to the two-stage combustion port 7 is increased by operating the

vessels

29a, 29b, 29c, 29d (step Sb4), and the oxygen concentration is increased to increase the heat recovery in a part of the furnace of the boiler 4, or the boiler 4 The amount of unburned matter contained in the exhaust gas is reduced in a part of the furnace.

Further, the present inventors have obtained the test results shown in FIG. 4 when adjusting the oxygen concentration supplied to the two-stage combustion port 7 in the test boiler for oxygen combustion of pulverized coal. As shown, the NOx concentration can be controlled so as to reduce the NOx concentration when the oxygen concentration to the two-stage combustion port 7 is lowered, and the oxygen concentration to the two-stage combustion port 7 is raised. Reveals that combustion with less unburned emissions in the exhaust gas becomes possible.

Thus, in the boiler 4 in which the burner 6 and the two-stage combustion port 7 are arranged, oxygen is supplied from the two-stage combustion port 7 to adjust the oxygen concentration, and the NOx concentration of the exhaust gas and the unburned content of the exhaust gas are adjusted. Emissions and furnace heat recovery can be controlled.

Further, in the embodiment, when the unburned amount of the exhaust gas is an allowable value and the total NOx concentration is lowered, the amount of recirculated exhaust gas to the second stage combustion port 7 is adjusted to increase by the flow rate regulator. In the case where the oxygen concentration to the two-stage combustion port 7 is decreased to increase the overall heat recovery of the boiler 4 or to reduce the unburned portion of the entire exhaust gas, the two-stage combustion port 7 is controlled by the flow controller. If the oxygen concentration to the second-stage combustion port 7 is increased by adjusting the amount of exhaust gas to be recycled to the second-stage combustion port, oxygen is supplied from the second-stage combustion port 7 to accurately adjust the oxygen concentration. Therefore, it is possible to suitably control the NOx concentration of the exhaust gas, the amount of unburned exhaust gas, and the heat recovery of the furnace.

Furthermore, in the embodiment, a plurality of two-stage combustion ports 7 provided in the boiler 4 are provided, and a plurality of branch oxygen supply lines 26a, 26b are provided so as to adjust the oxygen concentration for each of the two-stage combustion ports 7. , 26c, 26d, when lowering the NOx concentration in a part of the furnace of the boiler 4, increasing the heat recovery in a part of the furnace of the boiler 4, lowering the amount of unburned emissions contained in the exhaust gas in a part of the furnace Corresponding to the case, oxygen can be supplied from the respective branched

oxygen supply paths

26a, 26b, 26c, and 26d, and the respective oxygen concentrations can be adjusted accurately, so that the NOx concentration of exhaust gas and the unburned amount of exhaust gas are discharged. Further, the heat recovery of the furnace can be controlled more suitably.

In addition, when a tertiary recirculation path 19 for supplying a part of the exhaust gas supplied from the secondary recirculation path 14 to the second stage combustion port 7 of the boiler 4 is provided, oxygen is easily supplied to the second stage combustion port 7. Therefore, the NOx concentration of the exhaust gas, the amount of unburned exhaust gas discharged, and the heat recovery of the furnace can be controlled easily and accurately.

The exhaust gas control method and apparatus for an oxyfuel boiler according to the present invention are not limited to the illustrated examples described above, and various modifications may be made without departing from the scope of the present invention.

Claims

A boiler provided with a burner and a two-stage combustion port, a part of the exhaust gas discharged from the boiler and recirculated is introduced into the mill as a primary recirculation exhaust gas, and the pulverized coal pulverized in the mill is A primary recirculation system that supplies the boiler burner with recirculated exhaust gas, a secondary recirculation system that supplies another part of the recirculated exhaust gas to the boiler wind box, an oxygen production apparatus, and the oxygen production A direct supply system for directly supplying a part of oxygen produced by the apparatus to the burner, and a secondary oxygen mixed system for supplying another part of oxygen produced by the oxygen production apparatus to the secondary recirculation system An exhaust gas control method for an oxyfuel boiler having a passage, wherein the oxygen concentration is adjusted by supplying oxygen to a two-stage combustion port of the boiler.
When the unburned amount of exhaust gas is an allowable value and the overall NOx concentration is lowered, the oxygen concentration at the two-stage combustion port is decreased by adjusting the direction to increase the amount of recirculated exhaust gas to the two-stage combustion port. When increasing the overall heat recovery of the boiler or decreasing the unburned content of the entire exhaust gas, adjust the direction to reduce the amount of exhaust gas recirculated to the two-stage combustion port and adjust the amount to the two-stage combustion port. The exhaust gas control method for an oxyfuel boiler according to claim 1, wherein the oxygen concentration is increased.
3. The exhaust gas control method for an oxyfuel boiler according to claim 1, wherein the oxygen concentration is adjusted for each of the two-stage combustion ports with respect to the plurality of two-stage combustion ports arranged in the boiler.
2. The exhaust gas control method for an oxyfuel boiler according to claim 1, wherein a part of the exhaust gas supplied through the secondary recirculation system is supplied to a two-stage combustion port of the boiler.
3. The exhaust gas control method for an oxyfuel boiler according to claim 2, wherein a part of the exhaust gas supplied through the secondary recirculation system is supplied to a two-stage combustion port of the boiler.
4. The exhaust gas control method for an oxyfuel boiler according to claim 3, wherein a part of the exhaust gas supplied through the secondary recirculation system is supplied to a two-stage combustion port of the boiler.
A boiler provided with a burner and a two-stage combustion port, a part of the exhaust gas discharged from the boiler and recirculated is introduced into the mill as a primary recirculation exhaust gas, and the pulverized coal pulverized in the mill is A primary recirculation system that supplies the boiler burner with recirculated exhaust gas, a secondary recirculation system that supplies another part of the recirculated exhaust gas to the boiler wind box, an oxygen production apparatus, and the oxygen production A direct supply system for directly supplying a part of oxygen produced by the apparatus to the burner, and a secondary oxygen mixed system for supplying another part of oxygen produced by the oxygen production apparatus to the secondary recirculation system And an oxygen supply system for supplying oxygen to the two-stage combustion port of the boiler, and a flow controller for adjusting the oxygen concentration disposed in the oxygen supply system And provided that Exhaust gas control apparatus of an oxyfuel combustion boiler to symptoms.
If the unburned amount of exhaust gas is an acceptable value and the overall NOx concentration is to be lowered, adjust the flow rate regulator to increase the amount of recirculated exhaust gas to the second-stage combustion port and adjust the amount to the second-stage combustion port. When decreasing the oxygen concentration and increasing the overall heat recovery of the boiler or reducing the unburned content of the entire exhaust gas, adjust the flow controller to reduce the amount of recirculated exhaust gas to the two-stage combustion port. The exhaust gas control device for an oxyfuel boiler according to claim 7, wherein the exhaust gas control device is configured to increase the oxygen concentration to the two-stage combustion port.
9. The oxyfuel boiler according to claim 7 or 8, further comprising a plurality of two-stage combustion ports arranged in the boiler and a plurality of branch oxygen supply systems so as to adjust the oxygen concentration for each of the two-stage combustion ports. Exhaust gas control device.
The exhaust gas control device for an oxyfuel boiler according to claim 7, further comprising a tertiary recirculation system for supplying a part of the exhaust gas supplied through the secondary recirculation system to the second stage combustion port of the boiler.
The exhaust gas control device for an oxyfuel boiler according to claim 8, further comprising a tertiary recirculation system for supplying a part of the exhaust gas supplied through the secondary recirculation system to a second-stage combustion port of the boiler.
The exhaust gas control apparatus for an oxyfuel boiler according to claim 9, further comprising a tertiary recirculation system for supplying a part of the exhaust gas supplied through the secondary recirculation system to the second stage combustion port of the boiler.